Failing build

[zorbasd]

Evently's build is failing for Go 1.7. It seems to be unable to load some of Machinery's dependencies for some reason.

[chadwpetersen]

It would seem like we should just remove travis go 1.7 build support. Does not seem like machinery supports Go 1.7. I also note that machinery fixed their versions to go 1.9.2 and 1.8.5 a few days ago. So not to sure if we should just support the same exact versions only. I think that would make a lot of sense if we do. So I suggest the fix for this would be to remove 1.7 and fix the versions of go to 1.9.2 and 1.8.5 which should resolve the build failure.